As a biological body state assessment device of the related art, a biological body state assessment device described in Patent Literature 1 is known. The biological body state assessment device described in Patent Literature 1 detects driver information, such as an eye closure time ratio reflecting vigilance, and driver information, such as a head vibration transmission rate reflecting the degree of attention concentration, calculates the average value and standard deviation of an individual driver of each piece of driver information, and assesses the drowsy state, the drowsiness-conflicting state, the concentration state, and the carelessness state of the driver on the basis of the average value, the standard deviation, and vehicle/driving environment information.